Method for the formation of RF antennas by demetallizing and RF antenna products formed thereby

ABSTRACT

A thin and flexible radio frequency (RF) antenna tag or label is disclosed which contains an RF circuit connected to an antenna which is created by demetallizing the area around the antenna pattern on a thin, metallized substrate such as a film or paper web. Antenna(s) may be formed on one or both sides of the substrate and can contain printed, holographic, optical variable device, diffractive, dot matrix, computer-generated holograms or computer-generated optical images. The demetallized RF antenna on the substrate can optionally further be transferred to a second substrate or web by means of a cold foil stamping process. The tag or label is thin and flexible, enabling a wide range of applications including RF tagging of anti-theft devices, product packaging of all types, credit cards, passports, admission tickets, stamps, vehicles, badges, fare cards, roadway tolls, customs and immigration checkpoints identification, and animal identification/tracking devices.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to the field of radio frequency (RF)tagging. More specifically, the invention relates to an improved methodfor creating an RF antenna on a lightweight, flexible substrate throughdemetallization of the substrate around the antenna pattern, leaving themetallized antenna.

[0003] 2. Background of the Invention

[0004] Radio frequency (RF) tagging or identification is one of manytechnologies for identifying and/or tracking objects. The RFidentification process requires that information be carried on asubstrate such as a tag or label containing an antenna. The antennaallows reception and transmission of radio waves. Typically, the tag orlabel containing the antenna reflects an incident RF carrier back to abase station. It radiates or receives energy and can be structured toradiate or receive energy over varying bandwidths.

[0005] The tag usually consists of a semiconductor chip containing RFcircuits, logic and memory and it also contains an antenna, theformation of which is the subject of this invention.

[0006] A number of methods of manufacture of RF antennas are well knownin the field. The principal known techniques for fabricating RF antennasinclude foil forming, dip brazing and electroforming of metallic-basedstructures. The antennas are generally loops of wire soldered to acircuit card or consist of metal etched or plated on a circuit card.Much of the prior art has produced thick, stacked and layered tags withcomponents mounted on cards and covered in plastic, resulting in a rigidpackage. None of the known systems provides for production of antennasof varying densities.

[0007]

[0008] More recent inventions have reduced both the cost and weight ofan RF antenna by creating antennas on thin flexible tags, Such a processis described in U.S. Pat. No. 5,528,222. This method embeds metal intothe substrate that forms the tag, which requires a high density depositof metal. The tag or label containing the antenna must then be laminatedto an additional substrate, resulting in a thickness of up to 50micrometers. Such a thickness creates a less flexible tag or label andrestricts its range of applications.

[0009] Another formation method is described in U.S. Pat. No. 4,220,956,in which the antenna array is created by etching a copper laminate thatis adhered to one side of a thin substrate. The structure describedclaims a total thickness of less than 0.005 inch, which can bemanufactured as a thin flexible, rollable, lightweight array. Theantenna is created using an etching process substantially the same asthat used for forming printed circuit boards and microstrip antennas. Inthis process, the resulting thickness still reduces the flexibility andapplicability of the tag or label.

[0010] None of these methods provides an approach to the design andfabrication of RF antennas that reduces cost, thickness, and weight ofthe antenna tag or label that also increases its flexibility to allowfor a virtually unlimited number of applications.

SUMMARY OF THE INVENTION

[0011] The present invention provides an improved method for formationof RF antennas, which comprises demetallizing the antenna design leavinga very thin metal layer or metal in varying densities on a singlesubstrate without lamination, resulting in an extremely thin, flexibletag, label or packaging material.

[0012] This invention thus provides an improved method of designingantennas on film or paper webs for use in radio frequency identificationand/or tracking. Specifically, this invention uses a film or paper web,which is metallized on one or both sides, and demetallizes the antennapattern on one or both of the metallized sides. This process uses a verythin layer of metal (usually 0.02-0.06 μm) and demetallizes the antennadesign or pattern in a uniform density or different densities in thesame antenna if required. Because the web thickness is on the order of25-50 μm, the addition of the antenna has no significant effect on thethickness, and therefore the flexibility, of the web material as a tagor label. Further, there is no requirement for lamination to a label ortag because the antenna is created by demetallizing the area around theantenna design right on the web surface which will later be cut intolabels or tags. The preprinted or plain label or tag web with itsprinted, holographic, optical variable device, diffractive, dot matrix,computer-generated holograms or computer-generated optical images on oneside becomes the only substrate required to carry the antenna with itsradio frequency circuit on the other side.

[0013] The image on the printed side of the label can be printed byflexographic, offset, rotogravure, letter press or any otherconventional printing method or can be a holographic, diffractive,optical variable, or diffractive dot-matrix pattern or image whichrequires metal on both sides. The web can contain holographic continuouswallpaper patterns, diffractive, optical variable devices, holographicand diffractive dot-matrix systems, or non-holographic images orpatterns on one side so a registration process is not required. Inaddition, the web can contain specific holographic or non-bolographicimages which require registration of the antennas to those images usinga registration process.

[0014] This invention therefore provides a method for demetallizing theantenna design on a metallized preprinted film or paper web used forcreating labels, tags or packaging. This results in lower cost toproduce the RF devices and increases the number of potentialapplications because of reduced label thickness and weight. Cost isreduced because there are fewer manufacturing steps required and fewermaterial costs. If the application is flexible or rigid packaging, thenthe antenna can be demetallized right on the material itself withoutfurther processing steps. If the application is a label or tag, theresulting label or tag is flexible, because it consists of only the filmor paper with an adhesive backing. The liner is peeled from the backwhen applying the label or tag to the item to be tracked or read.

[0015] This invention represents an improvement over the prior art inseveral ways. It simplifies the manufacturing process for RF devices.Only one substrate is required for this process, which can be any typeof film, paper, or other web material. It also reduces the cost ofproducing RF devices because of the reduction in material costs and theelimination of production steps. Less metal is deposited and yet canproduce any type of antenna, and the need for additional materiallaminated to the antenna is eliminated.

[0016] In addition, because the lamination process is eliminated andonly one substrate is required, the tag or label produced is extremelythin and flexible. This creates a tag or label flexible enough for usein variety of both flexible and rigid packaging materials. For example,a flexible RF label can be applied to a bottle or box as a seal orauthentication device and it will conform to the package because of itsflexibility.

[0017] This invention represents an improvement over prior art becauseit allows for the creation of any type of antenna pattern and a moresophisticated array because of the ability to demetallize a singleantenna in varying densities if required. In addition, it also allowsthe demetallization of antennas on one or both sides of a metallizedsubstrate. These antennas can be different types and can be demetallizedin different densities or they can be the same antenna type and density.If having antennas on both sides of a substrate is the desiredapplication, then the antennas must be demetallized in register to eachother. These antennas can share the same RF circuit or each antenna canhave a different RF circuit for different applications.

[0018] The antennas in the present invention can include, reveal or bein register with images created by any desired type of process includingholographic, optical variable, dot matrix, diffractive, computergenerated holographic, computer-generated optical elements or otherknown means. Such images, particularly the holographic images, may beplaced on the antenna by printing or optical image formation using knownembossing, casting or injection molding methods. For instance, anantenna itself can contain holographic images if the metallizedsubstrate is embossed prior to demetallization of the antenna pattern.The holographic image can contain microtext or hidden images on thesurface of the antenna which results in the antenna acting as anaesthetic image, a security device and an RF tracking/identificationdevice all in one.

[0019] If the antenna patterns are produced for packaging applications,a package can be created that contains multiple RF antennas produced onthe same film web. Each antenna can have different applications ifdesired. Packaging of this kind can result in an antenna of continuouswallpaper design or the antenna can be demetallized on the web packagingmaterial in a specific area. Packaging of this kind can result inantennas in a continuous wallpaper design or antennas can bedemetallized on different package types; for example, flexible packagingused in food snack bags or rigid packaging used for cosmetic boxes.

[0020] This invention also allows for the creation of antennas throughthe demetallization process using a cold foil stamping method.

[0021] Applications for this invention include, but are not limited to,labels and seals to track virtually anything, memory chips that cancontain substantial information about the products they are applied to,verification or identification devices for purchases through theInternet (for example, event tickets), grocery store products, RF IDtagging of anti-theft devices, product packaging of all types, creditcards, passports, admission tickets, stamps, vehicles, badges, farecards, roadway tolls, customs and immigration checkpoints, and animalidentification/tracking devices.

[0022] Other features and advantages of the present invention will beapparent from the following more detailed description of the preferredembodiments taken in conjunction with the accompanying drawings, whichillustrate by way of example the principles of the invention. The scopeof the invention is not, however, limited to these preferredembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a plan view of a typical RF antenna configuration.

[0024]FIG. 2 is a plan view of the RF antenna of FIG. 1 shown positionedon the web backing that creates the tag or label.

[0025]FIG. 3 is a cross-sectional view taken on Line 3-3 of FIG. 2.

[0026]FIG. 4 is a schematic diagram illustrating an example of a singleRF antenna demetallized in different densities.

[0027]FIG. 5 is a schematic diagram illustrating an RF antenna inregister with a preprinted image on the opposite side of the substrate,and also illustrating a holographic image embossed on the surface of theRF antenna.

[0028]FIG. 6 is a cross sectional view of a web containing antennas onboth sides with holography on one of the antennas and an adhesive andsiliconized release paper attached to form a label or tag.

[0029]FIG. 7 is a schematic diagram illustrating the creation of RFantennas through the demetallization process on a standard printingpress.

[0030]FIG. 8 is a schematic diagram illustrating packaging applicationsfor the demetallization of antennas such as food packaging with multipleantennas in a wall paper configuration.

[0031]FIG. 9 is a schematic diagram similar to FIG. 8 and illustratinganother packaging application such as an antenna in registration with aspecific surface area of rigid packaging, such as a box.

[0032]FIG. 10 is a schematic diagram illustrating a cold foil stampingprocess for creating antennas.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS

[0033] The invention is best understood by reference to the drawings. Inthe basic process of this invention, a film or paper web, which may ormay not contain preprinted or embossed images upon it, and which ismetallized on one or both sides, is sent through a demetallizationprocess on a printing press to create RF antenna(s) on one or both sidesof the web.

[0034]FIG. 1 is a plan view of a radio frequency (RF) antenna 10 whichcontains junction areas 12 for connection to conventional RF antennacircuitry. FIG. 2 is a plan view of the RF antenna 10 of FIG. 1 tagformed by demetallization on the surface of a substrate 14, in themanner to be described below. The substrate 14 will be a paper or filmweb and which contains a metallized layer 16 (see FIG. 7) on one or bothsides, from which the RF antenna(s) are formed. The combination of theweb and the antenna(s) can be used for conventional RF tags or labels.The metal 16 used for metallization of the web material can be aluminum,copper, silver or other conductive metal depending upon the RFapplication. Commonly the thickness of the demetallized antenna is0.001-0.25 μm, preferably 0.02-0.06 μm, depending upon the requiredapplication. The thickness of the resulting tag or label is 10-100 μn,preferably 20-50 μm. The antenna thickness is normally <2%, preferably<1%, of the tag or label thickness, so for practical purposes thethickness of the tag or label can be considered to be the thickness ofthe substrate itself.

[0035] The demetallization is schematically illustrated in FIG. 3, whereportions 16′ of the metal layer 16 are shown as removed, leaving the RFantenna 10 formed as the residual metal layer 16. It will also be seenfrom FIG. 4 that the degree of demetallization can be controlled suchthat while the portions 16′ of the metal layer which are not wanted areremoved completely, other portions can be demetallized to greater orlesser degrees This is accomplished by variation according to thepattern on the face plates of the demetallization roller 30. The etchant34 may at any point remove the entire local depth of the metal layer, ormay merely thin it in a greater or lesser amount. The demetallization inany local area can therefore result in one or more lines, dots or othershapes where the metal is removed or thinned, or an array of smalladjacent regions of metal and metal removal, in patterns analogous tohalftone printing with inks. Thus it is possible to formed an RF antennawith, for instance, different portions 10 a, 10 b, 10 c, 10 d, 10 e, 10f and 10 g, being of different metal densities.

[0036]FIG. 7 illustrates the creation of antennas 10 directly on ametallized web substrate 14 by using a demetallization process on astandard printing press with specialized stations that are modified verysimply to allow for demetallization and washing. A continuous film orpaper web 14 which has been metallized on one or both sides with metallayers 16 is unwound from a continuous roll 18. The web 14 moves to thedemetallization station 20 along the press rollers 22 and 24. At thedemetallization station, the web moves through a series of press rollers26, 28, 30 and 32. The demetallization station 20 is essentially aprinting station as might normally deposit ink, but in this casedeposits a caustic substance or etchant 34 from tank 36, capable ofremoving specific portions 16′ of the metal 16 from web material 14.This chemical etchant 34, usually sodium hydroxide (NaOH) in solution,is deposited onto the web 14 around the antenna pattern or design asdetermined by the design/printing plates mounted on roll 30, thusremoving the metal 16′0 from the substrate 14 in a pattern around eachantenna 10, so that the antenna 10 itself remains metallized. Theetchant 34 oxidizes the metal to powder in the areas applied. The web 14is then routed by roller 38 to a washing station 40 where the powder isremoved by washing in water 42. The web 14 then travels past a dryingstation where a heat source 44, for example an infrared lamp, removesall water 42 from the web surface. The web 14 is then routed by rollers46 and 48 to rewinding cylinder 50 where it is rewound into a roll.

[0037] The web 14 containing the antennas 10 is sent to an RF deviceinstallation machine where conventional RF circuitry (not shown) isattached to the antennas through connection areas 12. After the RFcircuitry is attached, the web with its antennas and RF circuitry can beprepared for label or tag applications by treatment on a standard presswhere adhesive 54 is applied and a siliconized paper or other releaseliner 56 is married through the adhesive to the label or tag. If the tagor label has an antenna 10 on only one side of the web 14 (as in FIG. 3)the adhesive will be applied directly to the side of the web 14 thatdoes not contain the antenna. If the web 14 contains antennas 10 and 10′on both sides of the web 14 (as in FIG. 6) the adhesive can be appliedto either side directly on the top surface of the antenna (e.g., 10′) onthat selected side. The web can then proceed through a standard kisscutting station where the web containing the antennas is cut into theappropriate size labels or tags. No lamination to another web orsubstrate is required.

[0038]FIG. 5 illustrates how a web 14 containing the antenna(s) to formthe labels or tags can also contain images 52 on the surface of theantenna which is on the side that is not part of a wallpaper or othercontinuous pattern. These sources of these images have been describedabove. The web 14 may also contain specific images 60 which must bealigned with the antennas 10 on the reverse side, so the antennas mustbe demetallized in register with the preprinted or embossed images 60 onthe opposite side of the web. (See FIG. 5.) Registration is accomplishedthrough use of registration indicia (“eye marks”) 58 and 58′ in aconventional printing manner. The registration process ensures that theremoval of the metal occurs exactly where it is desired in relation tothe printed or embossed images. The process described in this inventionhas significant security applications as well as packaging enhancementapplications.

[0039]FIG. 7 also illustrates the demetallization-registration processon a standard printing press. The image-printed continuous film or paperweb 14 has been metallized on one side by metal layer 16 withregistration marks 58 and 58′ already printed next to one or more ofimages 60 (indicated as covered by the metal layer 16 in the inset). Ifit has been rewound into a roll (also represented by 18) after theprinting or embossing, it must be unwound from the continuous roll 18with the metallized side up. As the web 14 moves to the demetallizationstation 20 along the press rollers 22 and 24, the registration or eyemarks 58 and 58′ on the web material 14 are read by a registrationsensor 64 which relays the information as a signal to thedemetallization station 20. At the demetallization station, the web 14moves through the bank of press rollers 26, 28, 30 and 32. The speed atwhich the web 14 travels is determined by the registration informationconveyed by the registration sensor 64 to the demetallization station 20and is controlled by a servo motor 66 attached to the demetallizationstation. The application of the registration information is determinedby a simple computer software program which causes the servo motor 66 tospin faster or slower depending upon the registration information. Theservo motor 66 then adjusts the speed of the demetallization stationroller 32 and thus the speed at which the web 14 travels in order toensure that the demetallization occurs exactly where designed inrelation to the original images 60.

[0040] The key aspect in this embodiment of the invention is theregistration process. Without the “reading” of the registration marks 58and 58′ on the preprinted images 60 and the antennas 10, the antennascannot be demetallized exactly where desired in relation to the originalimages. Fiber optic, laser, and other sensors or sensing devices 64 arereadily available from sensing device vendors, readily identified bypublications such as the Thomas Register.

[0041] The washing station 40 for removal of the oxidized metal 16′ alsouses a standard inking station, in which the washing solution 42 iswater.

[0042] The drying station with heating device 44 is standard equipmenton flexographic presses for drying inks.

[0043] Because RF antennas are widely used, applications for thisinvention include, but are not limited to, labels and seals to trackvirtually anything, memory chips that can contain substantialinformation about the products they are applied to, verification oridentification devices for purchases through the Internet (for example,event tickets); grocery store products, RF ID tagging of antitheftdevices, product packaging of all types, credit cards, passports,admission tickets, stamps, vehicles, badges, fare cards, roadway tolls,customs and immigration checkpoints, and animal identification/trackingdevices.

[0044] An example of an enhanced security application is a securitylabel containing an image where the owner wants to ensure the productlabel cannot be counterfeited in addition to having an RF antenna fortracking or identifying the product. A design or pattern is selectedthat can be “hidden” in the original image by demetallizing a selectedarea, image or part of an image that may not be detectable to theunaided eye. In the case of a holographic image, a section containing ahidden code, numbers, or microtext may be demetallized or the areaaround a code, number or microtext may be demetallized. The RF antennaitself may contain a holographic image, within which can be a hiddencode, numbers, or microtext.

[0045] Examples of two applications of use of the RF antenna tags orlabels are shown in FIGS. 8 and 9. FIG. 8 shows a tag or label 110containing RF antennas 10 placed in a “wallpaper” patten on a flexiblesubstrate such as a potato chip bag 112. Similarly FIG. 9 shows a tag orlabel 118 containing a single antenna 10 placed in registration with aspecific location on a box 114, in this case a corner 116 of the box.Either or both of these of course can be done on many different types offlexible or rigid packaging such as boxes, bags or other containers forproducts or on the products themselves.

[0046] It is also contemplated that demetallizing an RF antenna can beintegrated with a cold foil stamping process. FIG. 10 shows this processin detail. A cold foil web 70 has demetallized antennas after exitingfrom the process of FIG. 7, and will have eye marks (equivalent to 58)for registration with a substrate 72, such as a paper web, to which thedemetallized antennas (“patches”) are transferred. The discrete areas ofadhesive 76 are applied to the substrate 72 at station 74. The adhesiveareas also have corresponding eye marks (equivalent to 58′) forregistration with the antennas. The web 70 and substrate 72 are alignedfacing each other by roller 78 at the entrance to station 80. Aregistration sensor 86 registers the antenna locations on web 70 bytheir eye marks and a similar sensor 84 registers the adhesive patternlocations on substrate 72 by their eye marks. Both sensors relay theirregistration information to indexing means 82, such as a servo motor,attached to press roller 88 located just before the alignment nip 90.The speed of foil web 70 is adjusted to ensure registration with thesubstrate 72 through the marrying zone 80. In zone 80 the two webs 70and 72 travel into the nip of press rollers 92 and 94 where the adhesiveareas 76 are pressure joined to the undersurface of the foil web 70,each in registration with a corresponding antenna. As the two marriedwebs pass the rollers 92 and 94 and reach the end of zone 80, theyencounter separation roller 96. The foil web 70 is curved around roller96 while the substrate 72 travels in a straight path causing theantenna/adhesive patches to peel away from the foil 70 and remainadhered to the substrate 72. The stripped foil web 70 is then wound ontotake-up roller 98 (which is rotated by a motor 100) where it iscollected for reuse, discard, or other purpose. The substrate 72, nowhaving on its surface the transferred antennas, continues on over guideroller 102 to take-up roller 104 (also driven by a similar motor 106)for collection.

[0047] The demetallization process described by this invention can beused on any type of film or paper and uses standard printing pressesincluding flexographic presses, rotogravure, letterpress and offsetprinting presses, and associated conventional equipment. These pressesrequire the addition of at least one registration setup includingregistration sensors, and the modification of a standard inking stationto perform the demetallization process. The equipment required to applythe method this invention can be purchased from standard printingindustry vendors, which also may be found in standard publications suchas the Thomas Register.

[0048] It will be evident that there are numerous embodiments of thepresent invention which are not expressly described above but which areclearly within the scope and spirit of the present invention. The abovedescription is therefore intended to be exemplary only, and the actualscope of the invention is to be determined from the appended claims.

I claim:
 1. A method for the formation of a radio frequency antenna of a predetermined pattern on a surface area of a substrate which comprises applying a metal layer to said substrate and thereafter removing that portion of said metal layer which comprises all metal within said surface area on said substrate other than metal of said metal layer disposed in said predetermined pattern comprising said antenna.
 2. A method as in claim 1 wherein said substrate comprises a plurality of said surface areas and removal of said portion of said metal layer comprises removal within each of said surface areas, such that a plurality of said antennas is formed with each antenna of said plurality being disposed within a respective one of said surface areas.
 3. A method as in claim 2 further comprising subdividing said substrate into a plurality of segments, each segment having contained thereon a single antenna.
 4. A method as in claim 2 wherein at least two antennas of said plurality of antennas are of different shapes.
 5. A method as in claim 2 wherein at least two antennas of said plurality of antennas are of different metal thicknesses or densities.
 6. A method as in claim 1 herein said antenna comprises at least two portions, one of said portions having a density of metal different from another of said portions.
 7. A method as in claim 1 wherein said substrate comprises a web material.
 8. A method as in claim 7 wherein said web material comprises film or paper.
 9. A method as in claim 1 further comprising placing an image on said substrate.
 10. A method as in claim 9 wherein said image is placed by printing or optical image formation.
 11. A method as in claim 10 wherein placement comprises embossing, casting or injection molding.
 12. A method as in claim 10 wherein said printing comprises flexographic, offset, rotogravure, letter printing.
 13. A method as in claim 10 wherein said optical image formation comprises formation of holographic, optical variable device, diffractive, dot-matrix, computer-generated holographic or computer-generated optical images.
 14. A method as in claim 1 wherein metal is placed on both sides of said substrate.
 15. A method as in claim 14 wherein said demetallization forms antennas on both sides of said substrate.
 16. A method as in claim 15 wherein different types of antennas are formed on each side of said substrate.
 17. A method as in claim 15 wherein the same type of antenna is formed on each side of said substrate.
 18. A method as in claim 1 further comprising placing an image on said antenna.
 19. A method as in claim 18 wherein said image is placed by optical image formation.
 20. A method as in claim 19 wherein placement comprises embossing, casting or injection molding.
 21. A method as in claim 19 wherein said optical image formation comprises formation of holographic, optical variable device, diffractive, dot-matrix, computer-generated holographic or computer-generated optical images.
 22. A method as in claim 1 further comprising subjecting said demetallized web containing said antenna to a cold foil stamping process whereby said antenna is transferred to a second web.
 23. A method as in claim 22 further comprising having registration indicia placed on said substrate and said second web and passing said substrate containing said demetallized antenna and said second web through a marrying zone in registration.
 24. A method as in claim 23 wherein said registration is accomplished by adjusting linear speed of either of said substrate or said second web relative to the other.
 25. A method as in claim 24 wherein adjustment of said linear speed is controlled by a microprocessor.
 26. An RF antenna article formed according to the process of claim
 1. 27. An RF antenna article as in claim 26 further comprising an RF antenna formed on the surface of a substrate.
 28. An RF antenna article as in claim 27, further comprising a tag or label.
 29. An RF antenna as in claim 28 wherein said antenna has a thickness on the order of <2% of the thickness of said tag or label.
 30. An RF antenna as in claim 29 wherein said antenna has a thickness on the order of <1% of the thickness of said tag or label. 